This invention relates to printing presses and more particularly to means for accurately controlling the amount of ink discharged from a printing press ink fountain to the printing press fountain roller.
In conventional printing presses, fountain keys are utilized to regulate the amount of ink which is discharged from the ink fountain into the fountain roller. This is achieved because a plurality of fountain keys are disposed along that edge of the fountain blade which lies adjacent the surface of the fountain roller. Normally, the fountain blade is biased radially outwardly from the surface of the roller and the fountain keys are used to overcome that bias to reduce the ink passageway formed between the edge of the fountain blade and the surface of the fountain roller. As the size of the ink passageway increases, a greater quantity of ink will be transferred to the ink roller and will appear on the final printed item as a relatively darker color. Conversely, when the ink passageway is reduced to its smallest size, virtually no ink is transmitted.
As is well known in the printing art, the set up of a press in order to run a printing job may, in larger presses, take a number of hours. This is because each of the many fountain keys in a particular printing press will have to be separately adjusted by the pressman before he can determine its correct setting for the job. Historically, the set up has been done on a trial and error basis, wherein each key is separately turned and adjusted until the final output is satisfactory to the pressman. The operation is repeated for every key disposed along the fountain blade.
This technique of set up includes working and reworking every fountain key along the fountain blade because there are internal stresses in the fountain blade which must be worked out by the pressman before the fountain blade can be set to run proper ink flow. This is done by working the keys to flex and unflex the fountain blade so that the blade may be finally relieved of all stresses and a uniform thickness of ink is transmitted to the fountain roller. As indicated, a great deal of time may be expended in properly setting the fountain keys for a particular run. Generally, only a very slight movement of the keys is necessary in order to obtain the desired flow of ink.
In U.S. Pat. No. 3,623,430, an apparatus for accurately determining the position of each of the fountain keys is disclosed. By use of the apparatus disclosed in this patent, the set-up time for a printing run is greatly reduced. A large calibrated dial is attached to each of the fountain keys. A pointer is provided for each of the dials, so that a pressman could note the relative position of each of the fountain keys. Thus, once a fountain blade was set up for a particular job, the positioning of each of the fountain keys could be noted then thereafter repeated if it were necessary to repeat the same job on the same press.
A problem encountered with the use of a plurality of fountain keys for adjusting the position of a fountain blade is that the fountain blade may torque during the set up processes. The torquing of a fountain blade is a commonly known problem in the printing art. The motion of a single fountain key upon a fountain blade can at times cause the fountain blade to torque or deflect, that is, twist along its entire longitudinal length or any portion thereof.
Also, when a single fountain key contacts and moves a portion of the fountain blade, it can also move not only the portion of the fountain blade adjacent the key but also any area of the blade extending to adjacent keys. This transfer of the motion of the fountain blade complicates the setting up process of the gap of the fountain blade, because the fountain key may have to be adjusted more than once to attain an accurately set gap.